An organic light emitting diode display is a self-emission display device which has one or more organic light emitting diodes that emit light to display an image. Because the organic light emitting diode display does not require a separate light source unlike a liquid crystal display, it is possible to reduce a thickness and a weight of the display device, as compared with a liquid crystal display. Further, because the organic light emitting diode display has high-quality characteristics such as low power consumption, high luminance, and a high response speed, organic light emitting diode displays have received attention as a next-generation display device for portable electronic apparatuses.
In general, an organic light emitting diode includes a hole injection electrode, an organic emission layer, and an electron injection electrode. In the organic light emitting diode, a hole supplied from the hole injection electrode and an electron supplied from the electron injection electrode are coupled with each other in the organic emission layer to form an exciton, and light is generated by energy generated when the exciton falls to a ground state. In the case of the organic light emitting diode, because self efficiency is not high, an internal resonance environment may be made in order to improve efficiency. However, in the internal resonance environment, because a path of light at the front is different, efficiency ratios of red, green, and blue are different from each other, and, as a result, a color difference (WAD) according to angles at the front and the side is generated (e.g., color shifts or brightness changes may appear based on viewing angle). In addition, because a large part of the light emitted from the organic emission layer is guided in a direction parallel to a laminated surface due to total reflection (e.g., total internal reflection) and is lost, light extraction efficiency may be low. Light extraction efficiency is a ratio of a quantity of light extracted from the diode at an observer (or viewing) side to an amount of light emitted from the emission layer, and because the organic light emitting diode has low light extraction efficiency, there is room for improvement with respect to characteristics of the display device such as luminance.
As such, various methods are being developed to improve the light efficiency by efficiently extracting the light generated in the organic emission layer and improving visibility by reducing the color difference (or color or brightness shifts)